Funds are requested to allow the purchase of updates and accessories for Varian MAT 311A and Finnigan MAT90 mass spectrometers which are needed to meet user demands for expanded capabilities in FAB and EI/CI analyses. The primary user group, which accounts for approximately 80% of the instrument time, consists of 15 NIH supported principal investigators awarded approximately $3.0 M annually, representing 10 different departments at three institutions. A secondary user group is also identified which have access to the instruments for 15-20% of the time. Updates and accessories being requested are divided between the two instruments and include, for the 311A, modifications for high mass range, high sensitivity operation in the FAB mode (magnet, flight tube and E sector), updates to the data system, a new FAB gun, a new heatable/coolable FAB probe and addition of a collision cell in the 1st FFR. The updates to the 311A would provide a state of the art FAB mass spectrometer-data system with a mass range to 5,000 u at 6kV versus a current mass range of 1400 u at 3kV. Updates to the MAT90 would expand the operating capabilities to include MIKES capability by addition of a collision cell in the 2nd FFR and to acquire spare ion volumns. In addition, a third color terminal is requested which would be shared by both mass spectrometers, resulting in increased utilization of both instruments, and a power conditioner needed to insure availability of clean power for the two instruments. Research areas of the users is broad, ranging from structure elucidation of low molecular weight natural and synthetic products to the identification of MH+ and sequencing of peptides and nucleic acid polymers with molecular weights greater than 1400u. Acqusition of the requested updates and accessories is, therefore, expected to have a significant, positive impact on research projects supported by the NIH, and other federal, state, local, industrial and private agencies at the University of Arizona.